Aftershocks from quake may be felt in the Valley

Temblor on fault line 1st major one in a century

Apr. 6, 2010 12:00 AMStaff and wire services

MEXICALI, Mexico - Aftershocks rattled the U.S.-Mexican border Monday in the aftermath of a major earthquake that killed two people, blacked out cities and forced the evacuation of hospitals and nursing homes.

Sunday's 7.2-magnitude quake, centered just south of the U.S. border near Mexicali, was one of the strongest earthquakes to hit the region in decades, shaking at least 20 million people.

Matt Fouch, a professor at Arizona State University's School of Earth and Space Exploration, said that, in the next few days, the Valley can expect to feel several aftershocks of up to 6 magnitude.

"Locally, it's still a problem," he said.

Scientists said the main earthquake, which had a shallow depth of 6 miles, probably occurred on a fault that has not produced a major temblor in over a century.

Preliminary data suggest the quake occurred on the Laguna Salada fault, which last unleashed a similar-size quake in 1892.

Since then, the fault has sparked some magnitude-5 temblors.

The human toll Sunday was minimal in large part because the energy from the quake moved northwest of Mexicali, a bustling commercial center along Mexico's border with California, toward a less-populated area, said Jessica Sigala, a geophysicist from the U.S. Geological Survey.

"We were just kind of lucky that the energy went the other way," Sigala said. "With every earthquake, the earth starts moving a certain direction. It started south of Mexicali, and the rupture moved northwest."

Still, at least 45 businesses and dozens of homes were destroyed and 233 people injured by falling objects in Mexicali, where the quake hit hardest, said Jose Guadalupe Osuna, governor of Baja California Norte.

Large cracks opened in the streets of Mexicali. Power lines fell, lampposts were bent, and furniture and merchandise were strewn around in shops and banks.

A 94-year-old man was killed when a wall collapsed in his home in the city, and a homeless man died when an abandoned home he was living in collapsed in a farming community, Osuna said.

Mexicali General Hospital was evacuated because of structural damage to the building, which also was without electricity and water.

Civil Protection Inspector Alan Sandoval said the most critical patients were moved to hospitals in Tijuana and the coastal town of Ensenada.

The parking garage still under construction at Mexicali's City Hall collapsed, but no one was injured.

The governor added that power had been restored to 75 percent of the city by midday and that water service was expected to be restored late Monday.

Across the border in Calexico, Calif., a home for seniors built in the early 1900s was evacuated and its residents moved to a Red Cross shelter.

Carlos Valdes, chief of the Mexican National Seismological Service, said improved building construction in northern Mexico limited the loss of lives in an area with a history of quakes.

"People see that it always shakes and have improved their construction capacity," Valdes said.

In the farming town of Guadalupe Victoria, the epicenter of the quake, roads buckled and some crevices opened several feet wide. People in the town of onion and asparagus farmers southwest of Mexicali are accustomed to earthquakes, but nothing prepared them for Sunday.

Esmeralda Quintana, a high-school teacher, said she will feel unsafe even at work.

"There are fallen trees, cables, light posts," Quintana said. "What's a safe place? We're in a place of earthquakes, but this one was tremendous."

Mike Conway, a state geologist with the Arizona Geological Survey, said the quake was caused by pressure building up on the North American and Pacific plates below the Earth's surface.

The plates created the San Andreas Fault, a source of numerous earthquakes in California.

An earthquake is caused when plates adjacent to each other suddenly slip, generating tremendous force.

Conway said it's "extraordinarily difficult" for scientists to predict when earthquakes will occur, but he said that, based on history, a major earthquake likely won't originate from the Mexicali area for a number of years.

The Associated Press and Republic reporter Craig Harris contributed to this article.